1. Field of the Invention
The present invention is related to a Front Opening Unified Pod (FOUP), and more particularly, to a FOUP disposed with a purgeable supporting module, a buffer gas chamber being disposed in the purgeable supporting module for gas to form a uniform gas flow field in the FOUP.
2. Description of the Prior Art
Semiconductor wafers need to be transferred by the automated system to different workstations to go through various processes in required equipments. In order to facilitate the transferring of wafers and to protect the wafers from external contaminants during the transferring process, a sealed container is provided for the automatic transferring process. Referring to FIG. 1, which is a view of wafer container of the prior art. The wafer container is a Front Opening Unified Pod (FOUP) that has a container body 10 and a door 20. The container body 10 comprises a pair of sidewalls 10L and a top surface 10T and a bottom surface 10B that are joined with the pair of sidewalls 10L, and an opening 12 is formed on one sidewall. A backwall 10B′ is formed on the other sidewall that is opposite to the opening 12, wherein a plurality of slots 11 are respectively disposed on the pair of sidewalls 10L for horizontally supporting a plurality of wafers. The door 20 further includes an outer surface 21 and an inner surface 22, wherein the door 20 is joined with the opening 12 of the container body 10 via the inner surface 22 to protect the plurality of wafers within the container body 10. Furthermore, at least one latch hole 23 is disposed on the outer surface 21 of the door 20 for opening or closing the FOUP. In the FOUP described above, the wafers are horizontally placed in the container body 10, and thus, a wafer restraint component is needed in the FOUP to prevent wafers from displacing or moving toward the opening 12 of container body 10 during the wafer transferring process due to vibration.
Referring to FIG. 2, which is a view of the structure of door 20 of a Front Opening Unified Pod disclosed in U.S. Pat. No. 6,736,268. As shown in FIG. 2, the inner side 22 of the door 20 is disposed with a recess 24. The recess 24 extends from the top end 221 of the inner side 22 to the bottom end 222 and is located between two latch mechanisms 230 (in the interior of the door). A wafer restraint module is further disposed in the recess 24, and the wafer restraint module is composed of two wafer restraint components 100 set side by side. Each wafer restraint component 100 includes a plurality of wafer contacts 110, which are used for sustaining corresponding wafers to prevent wafers from displacing or moving toward the opening of the container body during the wafer transferring process due to vibration.
The aforementioned slots 11 on two sidewalls 10L of the container body 10 and the wafer restraint module on the inner surface 22 of the door 20 are respectively used for supporting and restraining the plurality of wafers carried in the interior of the wafer container. However, friction between these supporters and restraint components and wafers occurs easily in the process of transferring the wafers and results in the generation of particles. When particles are generated in the container body 10 of the wafer container, they may remain on the surface of wafers or contaminate the wafers and thus cause decrease in chip yield. Therefore, wear-resistant materials are usually used when designing supporters and restraint components of wafer container to prevent from the generation of too many particles when the supporters and restraint components are in contact with the wafers. As shown in FIG. 3, which is a sectional view of the supporting module disposed on two sidewalls of the wafer container disclosed in US Patent No. 2006/0283774. The supporting module comprises a plurality of supporters 500 vertically arranged at intervals, and the surface of the supporters 500 is coated with a resin layer 501. The resin layer 501 has low-friction property and can prevent from generation of particles due to friction between supporters 500 and the wafers. However, in this design, since the resin layer 501 includes a bevel, wafers are only supported near the edges when being supported by the resin layer 501 of supporters 500. Thus when the scale of wafers is larger, drooping or sinking of wafers occurs more easily, which not only makes it easier for cracks of wafers to occur but also results more easily in chips or damage to wafers when wafers are transferred by the robotic arm.
Furthermore, certain components are disposed in the interior of the wafer container in some designs; for example, an outgassing opening or slit is formed near the contact area of wafers and the aforementioned supporters or restraint module for carrying particles generated due to friction away from wafers. As shown in FIG. 4, which is a view of the purgeable supporting module that can be disposed inside a wafer container as disclosed in the U.S. Pat. No. 6,899,145. The purgeable supporting module comprises a hollow main body 600, which is fastened to the sidewall of the container body of the wafer container and includes a plurality of vertical supporters 601 extending toward the interior of the container body, the plurality of wafers in the container body being supported by the plurality of supporters via the upper surface 602. A horizontal bar-shaped slot is formed on the side surface 603 of the supporters, from which gas in the hollow main body 600 is expelled to prevent the particles generated due to friction from forming on the surface of the wafers. In the aforementioned structure, as the bar-shaped slot is disposed on the side surface 603 of the supporters 601, it is more possible that the supporting force may be insufficient and thus displacement or overlapping of wafers that cause severe damages of wafers may occur more easily. Moreover, when the wafers are carried by the supporters 601 via the upper surface 602, the contact area between the wafers and the supporters 601 is rather large and makes it easier for particles to generate. In addition, the length of the bar-shaped slot is about the same as the length of wafers, and therefore the gas flow may be too weak and larger purging equipment is needed to provide a larger amount of gas to form gas flow field that functions effectively enough. Thus, a purgeable supporting module with a more comprehensive design is needed to be disposed in the wafer container so that particles can be effectively prevented from generating and forming on the surface of the wafers.